JP2001076993A - Exposure method and scanning exposure system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a rotationally a symmetric aberration in a projection optical system, which occurs due to exposure, by making a luminous flux incident on the projection optical system while a first object and a second object are scanned at a velocity ratio corresponding to the projection magnification of the projection optical system. SOLUTION: A reticle stage is moved before regular shot exposure and a lens illumination mark 103 is brought to a standstill under the rectangular illumination area 125 of an illumination system 101. Then, preliminary exposure for continuously exposing the lens illumination mark 103 for prescribed time is executed. The lens illumination mark 103 is constituted of a luminous flux divergent element, illumination light from the element is set to be divergent luminous flux and it is made incident on the respective lenses of a projection lens PK so that it becomes rotationally symmetric with respect to an optical axis. Thus, the illuminated range 120 of the lens 104 is illuminated so that the lens 104 is set to be rotationally symmetric and the whole lens is made to be a thermally saturated state. Even if illumination light which is not rotationally symmetric is received at the time of regular shot exposure, the occurrence of asymmetric aberration such as astigmatism is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and a scanning type exposure apparatus using the same. For example, a photomask pattern (reticle pattern) is scanned on a wafer by scanning the mask and the wafer in synchronization with a projection optical system. Exposure is suitable for manufacturing semiconductor devices such as ICs and LSIs, imaging devices such as CCDs, display devices such as liquid crystal panels, and devices such as magnetic heads.

[0002]

2. Description of the Related Art Recent advances in semiconductor device manufacturing technology have been remarkable, and fine processing technology has been accompanied by remarkable progress. In particular, the optical processing technology mainly uses a reduction projection exposure apparatus with a submicron resolution and a so-called stepper. To further improve the resolution, the numerical aperture (NA) of the optical system is increased and the exposure wavelength is shortened. ing.

[0003] In addition, a conventional scanning exposure apparatus of the same magnification using a catoptric projection optical system is improved, and a refraction element is incorporated in the projection optical system and a combination of a reflection element and a refraction element or only a refraction element is used. Using the configured reduction projection optical system,
A scanning exposure apparatus that synchronously scans both a mask stage and a stage of a photosensitive substrate (wafer stage) at a speed ratio corresponding to a reduction magnification has also attracted attention.

FIG. 8 is a schematic view of a main part of a conventional scanning exposure apparatus. In FIG. 1, a mask 1 on which a pattern (original image) is drawn is supported by a mask stage 4, and a wafer 3 as a photosensitive substrate is supported by a wafer stage 5. The mask 1 and the wafer 3 are placed at optically conjugate positions via the projection optical system 2, and a slit-shaped exposure light 6 extending in the Y direction in the drawing from an illumination system (not shown) illuminates the mask 1, An image is formed on the wafer 3 at a size corresponding to the projection magnification of the projection exposure system 2.

In the scanning exposure, the mask exposure is performed by moving both the mask stage 4 and the wafer stage 5 with respect to the projection optical system 2 in the X direction by a driving means at a speed ratio corresponding to the optical magnification. 1 and the wafer 3 are scanned, and the entire surface of the device pattern 21 on the mask 3 is transferred to a transfer area on the wafer 3.

[0006]

A step-and-scan type projection exposure apparatus (scanning exposure apparatus) has a slit-shaped exposure area, and a shot optical system scans a reticle and a wafer with a projection optical system. It is done by doing. When the scanning exposure of one shot is completed,
The stage on which the wafer is placed is moved by a predetermined amount, and scanning exposure of the next shot on the wafer is performed. This is repeated to expose the entire wafer.

In a scanning type exposure apparatus, since the exposure area is rectangular (slit-shaped), each lens member of the projection lens illuminated by the exposure has a rectangular shape or a rectangular shape depending on the place where they are arranged. It is illuminated with an elliptical light beam swelled by the spread of the illumination light beam and heated.

As the exposure progresses, such a heating environment causes the projection lens to be rotationally asymmetrically deformed. as a result,
There is a problem in that the image-forming light beam on the wafer generates astigmatism (astigmatism) and significantly deteriorates transfer characteristics.

The tendency is that the printing wavelength is i-line (365 nm).
As the wavelength becomes shorter from the wavelength to the far ultraviolet region (248 nm, 193 nm), the light energy becomes more prominent because the light energy is physically easily absorbed by the glass material.

In connection with this, Japanese Patent Laid-Open No. 10-50585
In the publication, an example of a solution is shown.

According to the present invention, there is provided an exposure method and an exposure method capable of easily producing a highly integrated semiconductor device by preventing or reducing the amount of rotationally asymmetric aberration by an effective method different from the invention of the publication. An object of the present invention is to provide a scanning exposure apparatus using the same.

[0012]

According to a first aspect of the present invention, there is provided an exposure method, wherein a mark provided on the first object side is illuminated with exposure light, and a slit-like light beam such as a rectangle or an arc from the mark is used to illuminate the mark. Illuminating a pattern of one object, causing the pattern of the first object to scan the second object by the projection optical system, and scanning the first object and the second object at a speed ratio corresponding to the projection magnification of the projection optical system; However, in the exposure method for projection exposure, a light beam is made incident on the projection optical system to thereby prevent or reduce the amount of non-rotationally symmetric aberration of the projection optical system caused by exposure.

According to a second aspect of the present invention, the pattern of the first object is illuminated with a slit-like light beam such as a rectangle or an arc.
An exposure method for projecting and exposing a pattern of a first object to a second object by a projection optical system while scanning the first object and the second object at a speed ratio corresponding to the projection magnification of the projection optical system. Illuminating a mark provided on the stage on the first object side, and causing a light beam from the mark to enter the projection optical system, thereby preventing the occurrence of asymmetric aberration of the projection optical system caused by exposure. It is characterized by.

According to a third aspect of the present invention, the pattern of the first object is illuminated with a slit-like light beam such as a rectangle or an arc.
An exposure method for projecting and exposing a pattern of a first object to a second object by a projection optical system while scanning the first object and the second object at a speed ratio corresponding to the projection magnification of the projection optical system. A mark provided on the first object is illuminated with light, and a light beam from the mark is incident on the projection optical system.
At least some lenses constituting the projection optical system are thermally substantially saturated.

According to a fourth aspect of the present invention, the pattern of the first object is illuminated with a slit-like light beam such as a rectangle or an arc.
An exposure method for projecting and exposing a pattern of a first object onto a second object by a projection optical system while scanning the first object and the second object at a speed ratio corresponding to the projection magnification of the projection optical system. A mark provided on the stage on the first object side is illuminated, and a light beam from the mark is incident on the projection optical system.
At least some lenses constituting the projection optical system are thermally substantially saturated.

According to a fifth aspect of the present invention, there is provided an exposure method comprising the steps of:
An exposure method for illuminating a pattern of an object and projecting and exposing a pattern of a first object to a second object by a projection optical system,
A mark provided on the first object side is illuminated with exposure light, and a light beam from the mark is incident on the projection optical system, thereby preventing or generating non-rotationally symmetric aberration of the projection optical system caused by exposure. It is characterized in that the amount is reduced.

In the exposure method according to the present invention, the first light beam is used.
An exposure method for illuminating a pattern of an object and projecting and exposing a pattern of a first object to a second object by a projection optical system,
A mark provided on the stage on the first object side is illuminated, and a light beam from the mark is made incident on the projection optical system to prevent the occurrence of asymmetric aberration of the projection optical system caused by exposure. And

In the exposure method according to the present invention, the first light beam is used.
An exposure method for illuminating a pattern of an object and projecting and exposing a pattern of a first object to a second object by a projection optical system,
A mark provided on the first object is illuminated with exposure light, and a light beam from the mark is incident on the projection optical system to thermally substantially saturate at least a part of the lenses constituting the projection optical system. It is characterized by being in a state.

In the exposure method according to the invention, the first light beam
An exposure method for illuminating a pattern of an object and projecting and exposing a pattern of a first object to a second object by a projection optical system,
A mark provided on the stage on the first object side is illuminated, a light beam from the mark is incident on the projection optical system, and at least a part of the lenses constituting the projection optical system is thermally substantially saturated. It is characterized by being in a state.

According to a ninth aspect of the present invention, in the invention of any one of the first to eighth aspects, the illumination of the mark provided on the first object side is performed before regular shot exposure or / and at a gap between shot exposures. It is characterized by having.

According to a tenth aspect of the present invention, in the first aspect of the present invention, the mark is provided on a movable stage on which the first object is placed.

According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, the mark is a luminous flux diverging element for generating a non-rotationally symmetric luminous flux.

According to a twelfth aspect of the present invention, in any one of the fifth to eighth aspects, the mark is a luminous flux diverging element for diffusing an incident luminous flux mainly in the scanning direction.

According to a thirteenth aspect of the present invention, in any one of the first to twelfth aspects, the light beam from the mark is incident on the projection lens in a region rotationally symmetric with respect to the optical axis of the projection lens. It is characterized by.

According to a fourteenth aspect of the present invention, in the invention according to any one of the first to twelfth aspects, the light beam from the mark is incident on the projection lens into an interpolation area of the irradiation area at the time of the shot exposure. It is characterized by having.

According to a fifteenth aspect of the present invention, there is provided a scanning exposure apparatus using the exposure method according to any one of the first to fourth aspects.

The exposure apparatus according to the sixteenth aspect of the present invention provides the exposure apparatus according to the fifth aspect.
9. The exposure method according to any one of items 1 to 8 is used.

According to a seventeenth aspect of the present invention, a pattern on a reticle surface is projected and exposed on a wafer surface by using the exposure method according to any one of the first to fourteenth aspects.
Thereafter, devices are manufactured through the developing process of the wafer. Method of manufacturing devices.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are schematic structural views of Embodiment 1 when the exposure method of the present invention is applied to a scanning type exposure apparatus.

FIG. 2 shows an irradiation range of exposure light of a scanning type exposure apparatus for comparison with the first embodiment of FIG. 1 and 2 are completely the same.

In this embodiment, a light beam emitted from a light source 100 is transmitted through an illumination optical system (illumination system) 101 to a reticle 10.
Step 2: irradiating the substrate 2 with a mask and projecting a circuit pattern formed in a reticle shape by a projection lens PL (projection optical system) while reducing and projecting the circuit pattern onto a wafer 108 coated with a photoconductor as a second object. The figure shows an AND-scan type exposure apparatus, which is suitable for manufacturing semiconductor devices such as ICs and LSIs, imaging devices such as CCDs, and devices such as magnetic heads.

1 and 2, an exposure light beam emitted from a light source 100 (laser or ultra-high pressure mercury lamp) is guided to an illumination system 101, and has a predetermined numerical aperture, illuminance, light intensity, uniformity, and irradiation area. Is converted into an illumination luminous flux having
The reticle (first object) 102 is illuminated.

In this case, as shown on the left side of the figure, the irradiation area 125 on the reticle 102 has a rectangular shape.
In the case of an inch reticle, it has a spread of about 104 mm × 132 mm. Reticle 102 is an optical system (projection lens)
Scanned against PL. (The scanning is performed in the direction of arrow 113 in the center of the figure.) In the scanning exposure apparatus of FIG. 2, while scanning the real element pattern area 150 of the reticle 102, mainly the lenses 1, 2, 3, and 4 in the projection lens PL are mainly used. 0 of illumination light flux (exposure light)
Only the portion existing in the space 119 through which the next light passes is strongly heated by the exposure.

FIG. 2B shows the lens 1 (10) near the reticle 102 where this tendency appears most strongly.
4 shows a cross section of FIG.

The shaded area of the lens 104 indicates the illumination area 116. The illumination area 116 on the lens 104 indicated by the hatched portion has a rectangular shape, indicating that only the central portion of the lens is heated. During normal shot exposure, the other lenses 105, 106 and 107 are in such a state. Since the individual lenses are originally mechanically kept rotationally symmetric, if such asymmetric heating continues, the lenses will undergo asymmetric deformation.

That is, the rectangular illumination area has a shape (toric surface) having different radii of curvature between the longitudinal direction and the lateral direction. As a result, astigmatism occurs as described above in the projection lens PL.

In the present embodiment, in order to avoid this, preliminary exposure is performed using the mark 103 provided on the reticle stage 102.

In this embodiment, as shown in FIG. 1, the reticle stage is moved before the normal shot exposure, and the lens illumination mark 103 serving as a preliminary exposure mark provided on the reticle stage is used as an illumination system. 101 is stopped under the rectangular illumination area 125, and the lens illumination mark 10
Preliminary exposure for continuously exposing No. 3 for a predetermined time is performed.

The lens illumination mark 103 may be located at any position other than the reticle stage 102a where illumination light is emitted. For example, as shown in FIG. 6, the lens illumination mark 103 may be used on the reticle 102.

FIG. 6 is different from the embodiment of FIG. 1 in that the mark 103 is provided on the reticle 102, and the other structures are the same.

In FIG. 1, the hatched area inside the projection lens PL indicates the illumination space inside the lens in this state. The diagram on the right corresponds to FIG.
The illumination area in the cross section of 4) is indicated by oblique lines.

In the present embodiment, the lens illumination mark 103 is constituted by a light beam diverging element, and the illumination light from the light beam becomes a divergent light beam and is incident on each lens of the projection lens PL so as to be rotationally symmetric with respect to the optical axis. Let me.

That is, as shown on the right side of FIG.
Is the illumination range 116 in the case of FIG.
Unlike this, the lens 104 is illuminated so as to be substantially rotationally symmetric. By performing the pre-exposure in this manner, the entire lens is brought into a thermally saturated state. This prevents asymmetrical aberrations such as astigmatism from being generated even when rotationally asymmetric illumination light is received during normal shot exposure (regular shot exposure).

FIG. 3 is a timing chart of the pre-exposure of this embodiment.

As described above, in the present embodiment, the pre-exposure mark (light diverging element) is arranged on the reticle movable stage and illuminated, and the light is diffused, diffracted, or scattered by the pre-exposure mark. In the projection lens, an area of glass that is not illuminated during the normal exposure (regular shot exposure) operation is illuminated and heated. Thus, the lens is maintained in a state of being thermally symmetrically heated, and the normal exposure operation is performed. This prevents the occurrence of asymmetric aberration in the projection optical system.

FIG. 4 shows a lens illumination mark (light diverging element) 1 as a mark for preliminary exposure applicable in this embodiment.
It is explanatory drawing of No. 03.

The lens illumination mark of FIG. 4A is a cross-sectional view when a deflection prism having a CC 'axis as a rotationally symmetric axis is formed. Within this section, the lens illumination mark 103
Is composed of a repetition of minute triangular prisms, and has the function of deflecting the incident light beam as shown by the arrow. In the area of the lens illumination mark 103, countless cell members as shown in FIG.

The lens illumination mark shown in FIG.
It has the same optical action as (A) but is composed of diffractive elements (binary optics) formed in layers.

FIG. 4C shows an example in which the same function is constituted by a light-shielding diffraction grating such as a chrome pattern.

The lens illumination mark shown in FIG. 4D is formed of a diffusion plate, and the directivity of transmitted light can be freely changed by adjusting the roughness.

Incidentally, as the luminous flux diverging element, a diffuser, a reciprocal grating, an optical wedge, binary optics, a lenticular plate, etc.
Anything that achieves the gist of the present invention is applicable.

FIG. 5 is a schematic view of a main part of Embodiment 2 when the exposure method of the present invention is applied to a scanning type exposure apparatus. The basic configuration of this embodiment is the same as that of the first embodiment in FIG. In the present embodiment, the illumination light beam at the time of preliminary exposure is not symmetrical to the optical axis of the lens (particularly the lens 1) as compared with the first embodiment of FIG. They differ in that they illuminate.
Then, the diagonal line divided into two inside the projection lens PL is
The optical path of the transmitted light of the lens illumination mark is shown. The shape of the illumination range may be any shape.

In the present embodiment, the normal exposure means that almost the entire surface of the lens is uniformly illuminated by applying interpolative illumination, and is heated and saturated. At the start of normal shot exposure, the lens is heated asymmetrically (rectangular). For example, when exposing the first wafer and carrying it out, the preliminary exposure of the present embodiment is performed. By doing so, the projection lens is symmetrically illuminated and heated, and the occurrence of asymmetrical aberration that is a concern can be suppressed. The timing at which the pre-exposure is performed is determined by the change characteristic of the lens with respect to heat.

For example, in the case of a projection lens having a high thermal sensitivity, it is necessary to perform a preliminary exposure for each wafer. However, in the case of a lens having a low thermal sensitivity, it is necessary to use several wafers, once per lot, or only at the beginning of a job. Preliminary exposure is sufficient. In the case of a wafer having a large number of shots per wafer, such as a 12 ″ wafer, the normal shot exposure may be interrupted during the exposure of one wafer to start the preliminary exposure operation.

The present invention is effective not only for the lens member in the projection lens but in the vicinity of the reticle like the lens 1, but also for the lens member near the pupil like the lenses 2, 3 and 4 in the drawing. It is.

Lens illumination mark 1 used in this embodiment
As an example of 03, a one-dimensional symmetric element having the axis cc 'as a line symmetry axis may be used in each of the optical elements of FIG. 4 introduced above.

The light for illuminating the mark may be light that does not expose the wafer having a different wavelength from the exposure light. Further, the present invention is not limited to the scanning type exposure apparatus, but is also applicable to a case where a reticle that generates non-rotationally symmetric aberration in a projection lens is used in a normal stepper.

FIG. 7 is a timing chart of the pre-exposure of this embodiment.

In the device manufacturing method of the present invention, a scanning type exposure apparatus using the exposure method of each of the above embodiments is used.
After aligning the reticle and wafer, the pattern on the reticle surface is projected and exposed on the wafer surface, and then
The wafer is manufactured through a development process.

[0060]

According to the present invention, when a pattern on a reticle surface as a first object is scanned and projected on a wafer surface as a second object in an exposure illumination area asymmetric with respect to an optical axis by a projection optical system. To achieve an exposure method and a scanning type exposure apparatus using the same, in which a pre-exposure that is appropriately set in advance is performed to prevent the occurrence of asymmetric aberration and easily manufacture a highly integrated semiconductor device. Can be.

In particular, according to the present invention, it is possible to suppress the occurrence of asymmetric aberration caused by exposure in an optical system having an asymmetric exposure illumination area such as a scanning type exposure apparatus.

Thus, even if the exposure load is increased, it is possible to continue printing without deteriorating the initial optical imaging performance.

Further, since the pre-exposure mark is arranged on the reticle stage, a dedicated reticle for pre-exposure is not required, and the mark can be exposed only by moving the stage. Therefore, the reticle exchange time is not required.

A device can be produced without reducing the throughput of the exposure apparatus. The effects such as that the total throughput of the semiconductor device can be significantly improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of a scanning exposure apparatus using an exposure method of the present invention.

FIG. 2 is a schematic diagram of a main part of a first embodiment of a scanning exposure apparatus using the exposure method of the present invention.

FIG. 3 is a flowchart of timing of pre-exposure in the exposure method of the present invention.

FIG. 4 is an explanatory view of a pre-exposure mark according to the present invention.

FIG. 5 is a schematic diagram of a main part of a second embodiment of the scanning exposure apparatus using the exposure method of the present invention.

FIG. 6 is a schematic diagram of a main part when a part of FIG. 1 is changed.

FIG. 7 is a flowchart of timing of preliminary exposure in the exposure method of the present invention.

FIG. 8 is a schematic view of a main part of a conventional scanning exposure apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 light source 101 illumination system 102 reticle 103 pre-exposure mark 104 to 107 lens PL projection optical system 108 wafer

Claims (17)

[Claims] 1. A first light beam having a slit shape such as a rectangle or an arc.
While illuminating the pattern of the object, the pattern of the first object is scanned by the projection optical system onto the second object, and the first object and the second object are scanned at a speed ratio corresponding to the projection magnification of the projection optical system. An exposure method for projecting and exposing a mark provided on the first object side with exposure light, and causing a light beam from the mark to enter the projection optical system, thereby causing a non-rotation of the projection optical system caused by exposure. An exposure method, wherein the occurrence of symmetric aberration is prevented or the amount of occurrence is reduced. 2. A first light beam having a slit-like light beam such as a rectangle or an arc.
While illuminating the pattern of the object, the pattern of the first object is scanned by the projection optical system onto the second object, and the first object and the second object are scanned at a speed ratio corresponding to the projection magnification of the projection optical system. In an exposure method for performing projection exposure, a mark provided on the stage on the first object side is illuminated, and a light beam from the mark is made incident on the projection optical system to reduce asymmetric aberration of the projection optical system caused by exposure. An exposure method characterized in that occurrence is prevented. 3. A first light beam having a slit-like light beam such as a rectangle or an arc.
A pattern of an object is illuminated, and a pattern of a first object is projected onto a second object by a projection optical system while scanning the first object and the second object at a speed ratio corresponding to a projection magnification of the projection optical system. In an exposure method for exposing, a mark provided on the first object is illuminated with exposure light, a light beam from the mark is made incident on the projection optical system, and at least a part of lenses constituting the projection optical system is heated. An exposure method characterized by being substantially saturated. 4. A first light beam having a slit-like light flux such as a rectangle or an arc.
A pattern of an object is illuminated, and a pattern of a first object is projected onto a second object by a projection optical system while scanning the first object and the second object at a speed ratio corresponding to a projection magnification of the projection optical system. In an exposure method for exposing, a mark provided on the stage on the first object side is illuminated, a light beam from the mark is incident on the projection optical system, and at least a part of the lenses constituting the projection optical system is heated. An exposure method characterized by being substantially saturated. 5. An exposure method for illuminating a pattern of a first object with a light beam and projecting and exposing the pattern of the first object to a second object by a projection optical system, wherein a mark provided on the first object side is exposed by exposure light. Irradiating a light beam from the mark onto the projection optical system to thereby prevent or reduce the amount of non-rotationally symmetric aberration of the projection optical system caused by exposure. . 6. An exposure method for illuminating a pattern of a first object with a light beam and projecting and exposing the pattern of the first object to a second object by a projection optical system, wherein the mark provided on the stage on the first object side is illuminated. And exposing a light beam from the mark to the projection optical system to prevent occurrence of asymmetric aberration of the projection optical system caused by exposure. 7. An exposure method for illuminating a pattern of a first object with a light beam and projecting and exposing the pattern of the first object onto a second object by a projection optical system, wherein the exposure light illuminates a mark provided on the first object. And exposing a light beam from the mark to the projection optical system to thermally at least partially saturate at least some lenses constituting the projection optical system. 8. An exposure method for illuminating a pattern of a first object with a light beam and projecting and exposing the pattern of the first object to a second object by a projection optical system, illuminating a mark provided on a stage on the first object side. And exposing a light beam from the mark to the projection optical system to thermally at least partially saturate at least some lenses constituting the projection optical system. 9. The method according to claim 1, wherein the illumination of the mark provided on the first object side is performed before regular shot exposure and / or in a gap between shot exposures. Exposure method. 10. The exposure method according to claim 1, wherein the mark is provided on a movable stage on which the first object is placed. 11. The exposure method according to claim 1, wherein said mark is a light beam diverging element for generating a non-rotationally symmetric light beam. 12. The exposure method according to claim 5, wherein the mark is a light beam diverging element for diffusing an incident light beam mainly in a scanning direction. 13. The exposure method according to claim 1, wherein a light beam from the mark is incident on the projection lens in a region rotationally symmetric with respect to an optical axis of the projection lens. 14. The exposure according to claim 1, wherein a light beam from the mark is incident on the projection lens into an interpolation area of an irradiation area at the time of the shot exposure. Method. 15. A scanning exposure apparatus using the exposure method according to claim 1. Description: 16. An exposure apparatus using the exposure method according to claim 5. Description: 17. A device is manufactured by projecting a pattern on a reticle surface onto a wafer surface by using the exposure method according to any one of claims 1 to 14, and thereafter subjecting the wafer to a development process. A method of manufacturing a device, comprising: